1. Field of the Invention
The invention relates to a vehicular accessory driving apparatus and, more particularly, to a vehicular accessory driving apparatus provided in a vehicle that has a plurality of engines.
2. Description of the Related Art
Japanese Patent Application Laid-Open Publication No. 57-76263 (pp. 2–4, FIG. 2) describes a vehicular engine arrangement that includes a main engine for driving the vehicle, and a subsidiary engine for starting and restarting the main engine and driving accessories, such as an alternator and the like (hereinafter, referred to as “auxiliary engine”).
The auxiliary engine drives accessories substantially all the time except the time of starting the main engine and the time of restarting the main engine. Therefore, during normal running of the vehicle, both the main engine and the auxiliary engine are operated. Specifically, the main engine drives the vehicle, and the auxiliary engine drives accessories.
In the case where the vehicle is driven by the main engine and the accessories are driven by the auxiliary engine, however, the amount of fuel consumed by the vehicle as a whole may become larger than in the case where the vehicle and the accessories are driven solely by the main engine. This is because operation of the auxiliary engine adds to the mechanical friction and the like. That is, if the amount of fuel consumed in the form of the friction loss and the like of the auxiliary engine is larger than the amount of reduction in the fuel consumption that is achieved by the auxiliary engine replacing the main engine in driving the accessories, the fuel consumption of the vehicle as a whole is larger than if the vehicle and the accessories are driven solely by the main engine.